Method for increasing propylene yield and gasoline yield through high-selectivity catalytic cracking

The invention relates to a method and a system for increasing propylene yield and gasoline yield through high-selectivity catalytic cracking. The method comprises the following steps: reacting a heavy raw material in a heavy oil cracking reactor and an enhanced catalytic conversion reactor, and separating to obtain a first product; separating the first product from the second product and the third product to obtain different fractions and the like; introducing the C4 liquefied gas fraction into a multi-branched olefin synthesis reactor for reaction, and separating to obtain an isobutylene-poor C4 material flow and a multi-branched olefin product; introducing the isobutene-poor C4 material flow and the light gasoline fraction into a high-cracking olefin synthesis reactor for reaction to obtain a high-cracking olefin product and an olefin-poor circulating material flow; enabling the lean olefin circulation material flow, the light gasoline fraction and the high-cracking olefin product to react in a light hydroc